For many years, communication and power lines have been carried above ground on spaced-apart poles placed along streets and right-of-ways. The trend in recent years, however, has been to enclose these lines in conduits which are buried below ground. Interchanges of these conduits are typically housed in subsurface vaults formed of cast concrete walls which are accessible through manhole openings. Typically, the manhole opening to the subsurface vault is defined by an annular cast iron frame which is attached to the concrete walls of the vault. A cast iron disk-like cover sits on a flange of the frame for closing the manhole opening.
While the cover is satisfactory for closing the manhole opening into the vault, there are problems which arise from use of conventional manhole covers to close openings to subsurface vaults. These problems include lack of significant resistance to unauthorized entry into the vault through the manhole and also water and debris infiltration into the vault. While the manhole covers used to close the manhole openings are typically heavy cast-iron disks, they are readily removed with pry bars and with relatively insignificant exercise of labor. Thus, access into unsecured manholes is relatively quick, and the communications and power cables are thereby easily accessible and at risk to vandalism. The relatively easy access through conventional manhole openings into the vault poses problems, as concerns regarding security for communication and power lines increase. Conventional wire lines are shielded but can be damaged by laborious cutting with tools. In contrast, fiber-optic lines are rather easily cut and damaged in a short time. Thus unsecured covers pose security risks due to the potential for unauthorized, but relatively easy, entrance into the vault.
Further, entry of water and dirt through the manhole opening into the vault also poses problems. The accumulated water in the vault can become contaminated by both devices in the vault and seepage of chemicals and contaminates into the vault. Conventional covers for manhole openings typically do not form perfect seals on the frame and storm water often leaks through the opening into the vault. Contaminants such as lead may leach into the water that collects in the vault. When work is to be done in the vault, the accumulated water must first be collected and tested for contaminates prior to disposal. Any contaminated water must be treated according to hazardous material regulations prior to disposal. Storage, handling, and treatment of the collected vault water is expensive, time consuming, and labor intensive.
Various devices and methods have been used to deter and delay access to vaults through manhole openings. One approach involves tapping a threaded bore into both the rim of the cover and the perimeter of the frame in which the cover sits. A bolt is screwed into the bore and thereby secures the cover to the frame. With this approach, however, the manhole would continue to experience ingress of water and debris into the vault. My prior application Ser. No. 08/665,287 filed Jun. 17, 1996 in the United States Patent and Trademark Office discloses a cap which facilitates authorized entrance and passage through the manhole opening, for example into a cable vault, while deterring unauthorized entrance and reducing ingress of water and dirt. In this cap, portions of a securing structure are received within the pan which defines the cap. Particularly, the securing structure comprises an elongate bar which has a pair of plate rigidly attached at distal ends. A threaded stud rigidly attaches intermediate the plates. The threaded stud extends through an opening in the pan and is secured thereto with a nut. The plates bear against a lower surface of a frame of a manhole opening in order to secure the pan to the manhole opening. An elongate flexible strand rigidly attached at a distal end of the threaded stud extends through the opening, in order to couple the elongate bar with the pan. The nut is received on the strand within the pan. A handle is attached to a second end of the strand, for pulling the strand through the opening and thereby bringing the threaded stud through the opening into the pan. The threaded stud has a transverse bore in a distal portion for receiving a shackle of a padlock in order to lock the cap in a secured position to the manhole opening. While the cap has met a need for permitting entrance into subterranean vaults while deterring unauthorized entrance and reducing ingress of water and dirt into the vault, the pans collect water and dirt. Particularly, the conventional manhole covers which are received over the pan do not prevent water and dirt from entering into the cap. The water and dirt plug up the padlock and the threads of the stud. The dirt and water have to be cleaned away in order to unlock the padlock, remove the nut, and release the cap from being secured to the manhole opening, whereby entrance to the subterranean vault is obtained.
Accordingly, there is a need in the art for a cap which facilitates entrance through a manhole opening to a subterranean vault while restricting ingress of water and dirt contaminants therein and shielding such contaminants from the structure that secures the cap to the manhole opening. It is to such that the present invention is directed.